Contact pressuring means for an electrical connector



May 21, 1968 J. A. NAVA 3,384,86fi

CONTACT PRESSURING MEANS FOR AN ELECTRICAL CONNECTOR Filed Sept. 3, 19652 Sheets-Sheet l INVENTOR. JOSZIPA/ 4. Mam

l 3 Y TTORNEYS .1. A. NAVA May 21, 1968 CONTACT PRESSURING MEANS FOR ANELECTRICAL CONNECTOR 2 Sheets-Sheet 2 Filed Sept. 5, 1965 INVENTOR.

JOSEPH ,4. Mm M ATTORNEYS United States Patent 3,384,866 CONTACTPRESSURING MEANS FOR AN ELECTRICAL CONNECTOR Joseph A. Nava, Villa Park,111., assignor to The Pyle- National Company, Chicago, 11]., acorporation of New Jersey Filed Sept. 3, 1965, Ser. No. 484,890 8Claims. (Cl. 339-256) ABSTRACT OF THE DISCLOSURE An electrical connectorhaving female socket portions and an opening formed in the wall of thesocket portions for positioning a contact spring therein. The openinghas fiat surfaces on opposite sides thereof, and the contact spring hasa beam section and reversely turned integral spring arms. The beamsection contacts the flat surfaces of the opening and the reverselyturned integral spring arms engage a shroud which is fitted over thesocket portion.

This invention relates to electrical connectors and particularly to apressurized electrical contact plate having inwardly directed cantileverspring arms and providing a contact force with a mating contact memberwhich is reduced at start of entry and increased at full engagement.

Electrical contacts are an essential component of many electricaldevices. Their purpose is to provide the means for disconnecting anelectrical circuit mechanically. The contact must perform itsconductivity function with a minimum of electrical resistance and withno detectable discontinuity within a time period of micro or nanoseconds when the contact is under mechanical stress such as vibration orshock.

To accomplish the conductivity function, the contact must be designedwith mechanical means for maintaining intimacy between two contacts in agiven circuit and with the ability to separate and reengage whendesired. Such separation and engagement must be accomplished rproducibly. The electrical characteristics such as electricalresistance, mechanical forces, and plating integrity must be maintainedfrom one engagement to another for hundreds and possibly thousands ofcycles. Only narrow limits of variations are permitted from the normaloperation specifications.

Furthermore, recent developments in circuit electrical requirement havemade reproducibility of the mating contact elements increasinglymandatory. For instance, the magnitudes of electrical circuitcharacteristics have been decreasing to the lower ranges of millivoltspotential and micro ampere currents. As these characteristics have dcreased, the precision with which the contacts must control theresistance through the contacting surfaces has greatly increased. Undersuch circumstances the associated contacts must maintain not only a lowresistance but a consistency of resistance which is the essence ofreproducibility.

While the need for reproducibility of contacts in certain electricalcircuits has become increasingly mandatory, the physical environmentsassociated with those circuits have become increasingly obstructive toobtaining that objective. For instance electrical connectors are nowbeing required to operate under temperatures up to 200 C. and undervibration and shock up to hundreds of Gs. The resulting strain on themating electrical members tends to develop a loss of continuity betweenthe contact surfaces which is the antithesis of contact reproducibility.

In addition to the need for reproducibility under con- 3,334,856Patented May 21, 1968 ditions of high physical strain, certain connectordesigns have required a decrease in the engagement force of theindividual contacts. The number of contacts associated with a givenconnector have increased steadily from 28 to and recently to 80. As aconsequence, the force re quired to couple and uncouple the connectorhas increased in direct proportion resulting in an increased wear on theconnector coupling mechanism. On the contrary a reduction in theindividual engagement force would correspondingly reduce the couplingforce and the wear on the associated coupling mechanism.

Accordingly, it is an object of this invention to provide a pressurizingmeans for improving the reproducibility of a pair of mated electricalcontacts.

It is also an object of this invention to provide a pressurizing meanshaving an improved contact continuity under conditions of high physicalstrain.

It is another object of this invention to provide mating electricalcontact members having a significantly reduced contact force at start ofengagement and an improved contact force at full engagement.

It is a further object of this invention to provide a pressurizing meansfor use with a shrouded contact socket having a substantially flatcontact plate and inwardly directed cantilever supported spring arms.

It is also an object of this invention to provide a pressurizing meansfor an electrical contact socket having a uniformly distributedengagement force with a mating contact member.

It is an additional object of this invention to provide a pressurizingmeans for an electrical contact socket which is responsive forcorrecting misalignment of a cooperable contact member.

Other objects and advantages of the present invention will becomemanifest to those versed in the art upon reference to the followingdetailed description and accompanying drawings wherein a preferredembodiment of an electrical contact having the characteristics of thepresent invention is illustrated.

On the drawings:

FIGURE 1 is an elevated view of an electrical contact socket and itsassociated circuit connection;

FIGURE 2 is a sectional view of a portion of the con tact socket of thisinvention as taken along the lines II-II of FIGURE 1;

FIGURE 3 is a cross-sectional view of the socket assembly of thisinvention as taken along the lines III- III of FIGURE 2 for illustratingthe mounting of a pressurizing means on the socket contact body;

FIGURE 4 is a diagrammatical representation of the mating relationshipof a contact pin and the pressurizing means of this invention forillustrating the force relationships existing at start of entry of thecontact pin into the socket of FIGURE 2;

FIGURE 5 is a diagrammatic representation similar to that shown inFIGURE 4 and illustrating the described force relationships duringpartial engagement of the contact pin and cooperable contact socket;

FIGURE 6 is a further diagrammatic view in the sequence characterized inFIGURES 4 and 5 and illustrating the force relationship between thepressurizing means and the contact pin during full engagement therewith;

FIGURE 7 is a force diagram illustrating the uniform force distributionassociated with the contact plate of this invention;

FIGURE 8 is also a diagrammatic representation of the responsive forcerelationship existing between the pressurizing means of this inventionand a contacting pin during misalignment of the cooperable contact members, and

3 7 FIGURE 9 is a graphical representation illustrating prior artpressurizing structures and the associated force relationship exerted ona contacting pin at various stages of engagement with a cooper-ablecontact socket.

As shown on the drawings:

Electrical contacts in an electrical connector are, generally, of a pinand socket configuration due to the density of contacts in theconnector. This requires that the contact mechanical features bedisposed axially along the length of the contact. Therefore, most pinand socket contacts consist of a pin which is generally a solid cylinderterminated to a circuit wire and a socket which is a hollow cylinderterminated to another wire representing the continuation of the circuit.Depending upon the design of the contacts, the pin or the socket mayprovide the mechanical means for providing intimacy between them.Experience shows, however, that the most reliable method is to providethe pressurizing means on the socket contact. This implies a springmember mounted on the socket, which will react mechanically with the pinwhen that pin is mated coaxially with the socket.

As shown on FIGURE 1, the socket contact of the present invention isindicated generally at 10 and comprises a tubular socket portion 11 anda plurality of stepped or recessed body portions 12, 13, 14, 15 and 16to accommodate assembled relationships with related connectorcomponents. However, any suitable structural configuration could beemployed without affecting the principles of the present invention.

The socket contact is also provided with a rear barrel port-ion 17having a recess or groove 18 for receiving a bared conductor wire. Aninspection hole 19 is provided to facilitate checking or inspection ofthe wire conductor within the recess 18.

The tubular socket portion 11 has an annular groove or recess 20 formedcircumferentially thereabout for providing a retaining function with acooperable shroud 21. The shroud 21 is crimped as at 22 about thereduced diameter provided by the recess 20 and extends coaxially aboutthe socket portion 11 to terminate a bell opening 23.

The tubular socket body 11 has a cylindrical bore 24 formed axiallythereof which is provided with a countersunk or tapered end opening 25disposed adjacent to the bell opening 23 of the associated shroud 21.The substantial alignment of the bell opening 23 and the tapered endopening 25 is provided to allow the insertion of a contact pin into thecylindrical bore 24.

To assure reproducible mating of a contact pin with the tubular socketportion 11, a pressurizing spring 26 p is disposed within the socket 24for maintaining a continuous load at the external surface of acomplementary fitted pin.

The pressurizin-g spring 26 comprises a substantially flat contact plate27 and a pair of cantilever spring arms 28 and 29 extending inwardlyfrom opposite ends of the plate 27. The spring arms 28 and 29 are formedintegrally with the contact plate 27 and are folded therewith to assumethe configuration shown in FIGURE 2. In folding the spring arms 28 and29 about the plate 27 rounded faces 30 and 31 are formed at the outersurface of the resulting crease. It is apparent from FIGURE 2 that therounded face 30- aids in the insertion of a contact pin within the bore24 by reducing the contact friction and hence the wear of the matingparts.

The pressuriz-ing spring 26 is mounted within the cylindrical bore 24 ata set of plane surfaces 32 and 33 milled substantially parallel to theaxis of the bore 24. The spring arms 28 and 29 are provided to havesufiicient tension to secure the pressurizing spring 26 between themilled surfaces 32 and 33 and the inner surface 34 of the shroud 21. Afeature of this mounting and of the configuration of the pressurizingspring 26 is that the contact plate 27 has a substantial width foroverlying the plane surfaces 32 and 33, while the spring arms 4 28 and29 have a substantially reduced width for extending against the innersurface 34 at a point significantly removed from the surfaces 32 and 33.This increased distance allows for a correspondingly increased springmotion between the contact plate 27 and the external surface of a matingcontact 10.

A further feature of the pressurizing spring 26 is found in roundedspring tips 35 and 36 formed at the outer extremities of the cantileverarms 28 and 29. The insertion of a contact pin within the cylindricalbore 24 will cause a gradual compression of the contact plate 27relative to the cantilever arms 28 and 29, and the rounded tips 35 and36 allow the cantilever arms 28 and 29 to pivot or roll about theircontact point with the inner surface 34 of the shroud 21. Therefore, thecontact of the tips 35 and 36 with the shroud 21 will not interfere withthe intended deflection of the cantilever arms 28 and 29.

One of the drawbacks of previous pressurizing devices has been that theengagement force, when a pin contact enters a socket contact is severaltimes higher than the extraction force. This is because the pin contactexperiences only a frictional force during extraction, whereas, theinsertion force is the sum of the frictional force plus the forcerequired to physically overcome the pressurizing means and displace itinto an axial position tangent to the pin contact.

This additional engagement force is totally unnecessary to themechanical and electrical function of the mated contacts. Its existenceincreases the coupling force of a connector assembly. In addition, andmore important, it increases the wear on the contacts because of itshigher value and also because of the shearing attitude between the endof the pressurizing means and the nose of the pin contact.

The force diagrams of FIGURES 4 through 6 illustrate the manner in whichthe present invention overcomes the drawback of previous pressurizingdevices. However, because of the variable nature of the spring, thecalculations illustrated conditions at the extreme positions. This makesit possible to describe the functional conditions without resorting tomathematical equations which define any and every state. In this way, itis possible to reduce discrete variables by elimination at specificconditions, although it is understood that such elimination is possibleonly at the stated extremes.

The extreme position illustrated in FIGURE 4 is the start of entry of apin 37 having a nose portion 38 irito the cylindrical bore 24. The nose38 of the pin 37 contacts the pressurizing spring 26 at the roundedsurface 30 provided by the fold between the contact plate 27 and thecantilever spring arm 26. .At this extreme, rotation of the springoccurs at the reaction pont F and F remains less than F; due to therotation. The transverse force seen by the pin 37 is derived bytherefore F =/zF For purposes of the foregoing equation, F is considerednegligible. It is apparent, therefore, that the transverse force whichthe pin 37 experiences is one-half the force which one cantileversection of the spring exerts. On the other hand, the force F as shown inFIGURE 4 related to the force P as shown in FIGURE 5 at full assemblyis:

F AF 2 This means that the present invention provides a spring whichexerts a force at entry which is A times the force at full engagement.

The spring attitude slightly past midpoint is shown in FIGURE 5 and thestatic force equation is as follows:

No moments exist and the force system achieves stability. At this pointP has increased from %(F1+F2) to the sum of F +F and is at a maximum.

To provide a comparison to other types of springs, it is necessary toperform similar analysis. Three typical spring designs are displayed inFIGURE 9 both graphically and analytically. All, except the presentdesign, show forces at entry substantially higher than 'at any otherpoint in the engagement sequence.

It is apparent from FIGURE 9 that the present design displays auniformly increasing force during entry to the full engaged force,without the obvious disadvantages of excessive initial forces.

The full engagement position shown in FIGURE 6 illustrates a balancedsystem with a concentrated load at F at the center of the flat beamsection. In practice, however, this is impossible since the flat beamwill deflect upon application of a load. The forces seen by the pincontact, therefore, become distributed across the full length of theflat beam from the center to the end thereof following orthodox stresspatterns.

Therefore, the present design provides a spring merriber w'ihchdistributes its force generally uniformly over the length of itsengagement portion with the pin contact.

The distribution of the engagement force over the extended contact plate27 is a decisive improvement over previous pressurizing means which havecharacteristically exerted their force on a concentrated area. Suchforces increase the unit pressure on the surface of the pin contact,thereby increasing the rate of wear of the associated parts. Thepressurizing spring of this invention reduces wear accordingly byredistributing concentrated forces over an extensive contact area.

In addition to the problems of high entry forces and increased wear dueto concentrated pressures on the contact surfaces, many pressurizingmeans are incapable of reacting to misalignment of the pin to the socketand producing forces which will bring the two into axial alignment. Theexistence of such misalignment has attendant with it, the conditionwherein the fulcrum between the pin and socket exists, allowing movementof the two relative to each other. This movement causes changes in theelectrical resistance of the contacts which is most undesirable.

This invention, however, provides a force system which creates areactive force responsive to the misalignment in excess of the normalengagement force.

I-f normal engagement forces are illustrated by FIG- URE 7 and amisaligned condition is further shown in FIGURE 8 it is apparent that anew force system has been created by the indicated misalignment. Inparticular, an additional force AF is developed at the rounded tip 35and the pin is reacted at p such that The uniqueness of this concept isthat not only does AF additional force occur, but it occurs in thelocation :and direction most necessary to correct the misalignment, andsimultaneously, p has moved from the center of the contact plate 27 tothe misaligned end. An equal, but opposite condition will prevail ifmisalignment occurs in the opposite direction in the same plane.

To further illustrate and identify the structural characteristcs of thespring, it may be noted that the beam section 27 terminates at axiallyspaced shoulder portions 27a and 27b. The spring arms 28 and 29 are of aconsiderably narrower width (FIGURE 3). Thus, the folded portions extendaxially outwardly from the respective shoulders 27a and 27b to form therounded faces 30 and 31, which, in functional effect, operates ascamming faces for engagement with an adjoining pilot portion of a pincontact such as the nose 38. The arms 28 and 29 are reservsely turnedfrom the folded rounded free portions 30 and 31 and extend towards oneanother at an inclination relative to the beam section 27, terminatingshort of engagement to leave a space 25.

Although minor modifications might be suggested by those versed in theart, it should be understood that I desire to embody within the scope ofthe patent warranted hereon all such modifications as reasonably andproperly come within the scope of my contribution to the art.

I claim as my invention:

1. A connector comprising:

a socket having a circumferentially extending wall for receiving a malecontact member,

said wall having an opening formed therein, the edges of said open-ingin said wall being formed by fiat surfaces on opposite sides thereof,

a contact spring in said opening including a fiat beam section engagingsaid fiat surfaces,

and a shroud sleeve on said socket for retaining said contact spring,

said contact spring including a reversely turned integral spring armdisposed angularly with respect to said beam section for engagement withsaid shroud sleeve and spring loading said beam section towards saidshoulders, and means on said contact spring engaging said socket tocause said contact spring to pivot towards said shroud sleeve at firstcontact of the male contact member with said contact spring when themale contact member is inserted into said socket to reduce the force onthe male contact member at entry relative to the force on the malecontact member at full engagement.

2. A connector as defined in claim 1 and further characterized by saidspring arm being formed of a narrower width than said beam section.

3. A connector as defined in claim 1 and further characterized by saidspring arm being formed of a narrower width than said beam section,

said spring arm being reversely turned at a folded portion extendingaxially from said beam section and then extending angularly to form arounded camrning face for sliding engagement with a male contact memberinserted into the socket. 5 4. A connector as defined in claim 1 andfurther characterized by said spring arm being formed of a narrowerwidth than said beam section,

said spring arm being reversely turned at a folded portion extendingaxially from said beam section and then extending angularly to form arounded camming face for sliding engagement with a male contact memberinserted into the socket,

there being a spring arm at each end of said beam section and therespective spring arms terminating short of engagement with each other.5. A female contact having an opening formed in the peripheral wallsthereof extending inwardly of its end,

said opening being fiat shoulders at opposite sides formed in saidwalls,

a shroud sleeve surrounding said contact, and a contact spring betweensaid sleeve and said opening comprising a fiat beam section of a lengthand width to engage the flat walls and extend chordally across saidopening, integral spring loading means to bias said beam section towardssaid shoulders, and said spring loading means consisting of a pair ofreversibly turned arms disposed angularly with respect to said beamsection and terminating short of engagement with each other, and meanson said contact spring engaging said female contact to cause saidcontact spring to pivot towards said shroud sleeve at first contact of amale contact member with said contact spring when the male contactmember is inserted into said female contact to reduce the force on themale contact member at entry relative to the force on the male contactmember at full engagernent.

6. A female contact as defined in claim 5 and further characterized bysaid arms being narrower in width than said beam section.

7. A female contact as defined in claim 6 and further characterized bysaid spring having a curved folded face portion between said beamsection and each said arm forming a camming surface to slidably engage'an adjoining male connector surface.

8. A generally cylindrical hollow contact having an axial opening in oneend for receiving a male pin,

said contact having an axially extending opening in the walls thereofforming a pair of flat shoulders in co-planar relationship,

means for applying spring pressure against the male pin comprising aspring member having a flat beam section engaging said flat shouldersand spanning the space therebetween,

and a pair of reversely turned spring arms disposed at an angle relativeto said beam section,

and a sleeve fitted over the slotted portion of said contact andcovering said spring member and clamping said spring arms to bias saidbeam section towards said flat shoulders and into engagement with themale pin, and.

means on said spring member engaging said contact to cause said springmember to pivot towards said sleeve at first contact of the male pinwith said spring member when the male pin is inserted into said contactto reduce the force on the male pin at entry relative to the force onthe male pin at full engagement.

References Cited UNITED STATES PATENTS MARVIN A. CHAMPION, PrimaryExaminer.

P. TEITELBAUM, Assistant Examiner.

